Electric condenser



May 28, 1957 J. H. NICHOLAS 2,794,053

ELECTRIC CONDENSER Original Filed Feb. 1, 1952 4 Sheets-Sheet l COND UCTION GLAZ E INVENTOR. James H. Tllcho las May 28, 1957 J. H. NlCHOLASELECTRIC CONDENSER 4 Sheets-Sheet 2 Original Filed Feb GLAZE CONDUCTIONINHENERI mes H. u: 0 06 J. H. NICHOLAS 2,794,063

ELECTRIC CONDENSER 4 sheets-sheet 3 Miy 28, 1957 Original Filed Feb. 1,1952 VOLTAGE DISTRIBUTION BETWEEN cououcmn 4 EXTERNAL GROUNDED SURFACEOF men 510511555 CONTROL TUBE,

INVENTOR. James H. Nicholas B 1 1/ I 1/ I z; 1 1 l C 1 C w w m WE .U Q C9C5 UM [4W HmwM D 4 A W N NL% ML 0 06 4 80 C C .4 4C

May 28, 1957 J. H. NICHOLAS ELECTRIC CONDENSER 4 Sheets-Sheet 4 GLAZE vCONDUCTION GLAZE INVENTOR. James H. nwholas Original Filed Feb. 1, 1952United States Patent ELECTRIC coNDENsER James H, Nicholas, Chicago,Ill., assignor to G & W

Electric Specialty Company, Chicago, Ill., a corporation of IllinoisOriginal application February 1, 1952, Serial No. 269,365,

now Patent No. 2,745,897, dated May 15, 1956. Divided and thisapplication April 8, 1953, Serial No. 347,500

Claims. (Cl. 174-143) This application a division of my co-pendingapplication Serial 269,365, filed February 1, 1952, issued as Patent No.2,745,897 on May 15, 1956.

This invention relates to electric condensers that are particularlyadapted for use in high voltage electrical potheads such as are used forterminating the end of an insulated conductor.

It is one of the objects of the present invention to provide means forcontrolling the potential gradient in the outer insulator of a potheador terminator structure to maintain as far as possible a uniform axialpotential gradient in the transition from the radial electric field tothe axial or longitudinal field.

The use, on extra high voltages, of potential gradient control meanssuch as have heretofore been employed in potheads up to 160 kv. wouldgenerally result in an extremely large porcelain tube or tubes, whichwould be very costly and inefiicient. A considerably greater length andlarger bore diameter would generally be required. Therefore, the abilityof the porcelain tube to withstand the high internal hydraulic or gaspressures employed on pipe type cable systems would be reduced. Therupture stresses might be so great as to make the design infeasible.

It is one of the objects of the present invention to provide a condenserthat is particularly adapted for controlling the external surfacepotential gradients in such a manner as to keep them at a more uniformvalue for the entire overall length of the porcelain of the pothead,thus using all of the surface with an equal and therefore highefficiency. In accordance with the principles of the present inventionthere is employed a ceramic tube of fairly rugged wall section and ofmaterial having an extremely high dielectric constant, that is, aspecific inductive capacity of 100 to 200. By properly applying aconducting media on the external surface of such a tube or cylinder avery effective radial stress control tube can be ob tained. This is sobecause the radial voltage division between two coaxial electrodesinsulated by two or more dielectric materials is not only a function ofthe various radii of the electrodes but also of the dielectric constantor specific inductive capacity (S; I. C.), and the thickness of thevarious dielectric materials. The higher the S. l. C. of one materialused compared to the S. I. C. of the other material the less voitage thehigher S. I. C. material has developed across it. Therefore, if theratio of the S. l. C. of the two materials is made quite high, say 50 or100 to one, then the high S. I. C. material will have a very smallpotential drop across it.

it is a still further object of the present invention to provide acondenser for controlling the potential gradient in the outer insulatorof a high voltage terminator, which condenser is of an annular shape sothat it can be slipped over the end of the high voltage conductor inassembling the terminator and wherein the condenser has a body ofinsulation constituting the dielectric of the condenser, which bodysurrounds the conductor and extends radially towards the outerinsulator. A still further object of the present invention is to providea simple and economical arrangement for making electrical connectionsbetween parts of adjacent gradient controlling capacitor units. This isaccomplished, in the preferred construction, by using circumferentiallyextending garter springs that surround each capacitor unit, each springbeing connected to the appropriate adjacent unit by a flexible jumperlead.

While the high voltage condenser of the present invention is primarilyintended for use on cable systems which depend upon high internalhydraulic or gas pressures for their statisfactory operation, theprinciples of the present invention are also applicable to potheads forlow pressure systems.

The attainment of the above and further objects of the present inventionwill be apparent from the following specification taken in conjunctionwith the accompanying drawings forming a part thereof.

In the drawings:

Figures 1 and 2, when placed end to end in axial alignment, are alongitudinal sectional View of a terminator embodying the presentinvention;

Figure 3 is a half elevational view and a half longitudinal sectionalview of a capacitor unit of the present invention;

Figure 4 is a plan view of the capacitor unit;

Figure 5 is an enlarged cross section through the conductor and gradingtube and shows the potential gradient therethrough;

Figure 6 is a diagrammatic view showing the approximate distribution ofthe equipotential lines in a terminator of the present invention; and

Figure 7 is a view similar to Figure 3 but showing an alternatecapacitor grading tube.

Reference may now be had more particularly to the drawings wherein likereference numerals designate like parts throughout.

in the high voltage cable terminator of Figures 1 and 2 a cable 1 ismechanically connected to the outer porcelain insulator of a pothead orterminator 2 in the same manner as shown and more fully described in mypending application Serial No. 219,294, filed April 4-, 1951, now PatentNo. 2,727,938, to which reference may be had. The means for sealing theend of a cable that enters the pothead may be the same as that shown anddescribed in my application above referred to.

The cable conductor is indicated at 3. It is covered with theconventional wrapped paper insulation and surrounded by a conventionaljacket 5 of insulation, of the type known as Polyethylene. in preparingthe end of the cable for connection within a cable terminator the jacketend of the cable is removed in the usual manner to terminate at 6, andthe cable shielding braid 7 is.removed to a point slightly above the end6. Thereafter a stress cone insulator 9 is formed around the wrappedpaper cable insulation 8. The stress cone insulator may be a preformedwrapping, known in the art. or may be formed in situ, as is also knownin the art. In the case of the preformed stress cone it consists of animpregnated wrapped paper tube tightened on the cable duringinstallation. The ground connection of the cable shielding braid 7 iscontinued by a wrapping of metal braid 10 which continues up to andslightly beyond the point of maximum diameter of the stress cone 9. Themetal shielding braid 16 is then covered by a wrapping of coverinsulation 11, all as described in the above referred to pendingapplication. The cover insulation 11 is preferably a wrapping that canbe compressed considerably without permanently distorting the same. Onesuitable material is a spongy crepe paper.

A stainless steel conical body 20 having a bottom flange 20a is securedat its lower end to the terminator mounting plate and suitably gasketedto provide a liquid-tight seal, and is grounded. A metal ring 21 iswelded within the body 26 for supporting the stress control structure tobe presently set forth. The ring 21 has a series of supporting bolts 22threaded thereinto and secured in place by lock nuts. Thesupportingbolts 22 are uniformly spaced from one another, there beingany suitable number of such bolts, six, eight or more. The supportingbolts 22 are of metal and support at their upper ends a base or seatingring 23 of metal, on which seating ring 23 the capacitor gradingequipment, to be presently described, rests. The body has a metal ring24 welded to the top thereof to facilitate securing the outer porcelaininsulator 27 in place, as by six, eight, or more bolts 28 that threadinto a one-piece ring 29 that is cemented to the bottom of the insulatorfor drawing the insulator firmly against a frusto conical sealing gasket29', all as shown in my application Serial No. 219,294, to whichreference may be had.

The capacitor grading equipment of the present invention comprises aradial stress unit 39 that rests on the seating ring 23 and in turnsupports a series, in this instance ten, of capacitor potential gradientcontrol units 32. The radial stress unit 30 is a hollow circular tube orsleeve of fairly rugged wall section, having lower and upper surroundingflanges 36-37. The material of which the tube is made is preferablyceramic, and of an extremely high dielectric constant (specificinductive capacity between 100 and 200). One suitable material, by wayof example, is titanium dioxide. A conductive glaze or coating 39 isformed on the outer cylindrical portion of the unit 34), coveringsubstantially the entire cylindrical surface of the inner sides of theperipheral flanges 36 and 37 where the metallic glaze terminates.

The top and bottom of the unit are formed as perfectly fiat surfacesparallel to one another and at right angles to the longitudinal axis ofthe unit.

The flanges 36 and 37 merge with the body of the unit along smoothcurves, free of sharp edges, so that the metal glaze on the outside ofthe unit is also free of sharp edges where it extends from thecylindrical portion to the flanged portion of the unit.

Each capacitor potential gradient control unit 32 comprises acylindrical body 40 of the same material as that of the radial stressunit 30 and also has upper and lower peripheral flanges, indicated at4l4l, that extend from the cylindrical body 40 along smooth curves freeof sharp edges. Midway between the short flanges 41-41 there is a ratherwide continuous peripherally extending flange 42 which is an integralpart of the rest of the unit 32 and surrounds the cylindrical body 40thereof, and terminates at its outer edge in a peripheral rim 44appreciably thicker than the flange 42. The rim 44 joins the flange 42along smooth curves, free of sharp edges, and the flange 42 likewisejoins with the cylindrical body 40 along smooth curves. A conductiveglaze or coating 46, of metal or other suitable material, is formed onthe outer cylindrical surface of the body 40 below the flange 42. Theconductive glaze covers the entire cylindrical portion between theflange 41 and the flange 42 and extends at 4-7 to cover the entireannular surface of the flange 42. This conducting glaze terminates at48. The rim 44 extends a slight distance beyond the end 48 of theconductive coating. At its lower end the conducting glaze terminates at49 radially inwardly of the outer end of the flange 41, so that theflange extends beyond the end 49 of the glaze around the entire body 32.The upper half of the unit 32 has a similar metallic glaze 46' formedtherein, identical in extent with the glaze 46, so that the upper andlower halves of the unit 32 are identical. The top and bottom surfacesof the unit 32 are flat, parallel planes so that similar units can beplaced one upon another with substantially no spaces between them. a

It is apparent from the above description that the two the upper andlower values.

metallic coatings 4646' and the capacitor grading unit 32 constituteplates of a condenser wherein the flange 42 constitutes the dielectric,and that the size and material of the flange determines the capacity ofthe condenser. In addition, the cylinder surfaces 46-46 are capacitycoupled with the cable conductor 3, the dielectric comprising thecylindrical body of the capacitor grading tube 343 or 32 and the mass ofinsulation between the unit 39 or 32 and the cable conductor.

In the pothead illustrated in Figures 1 and 2 there are ten capacitorgrading units 32 stacked one upon another, the lowermost one resting onthe grounded radial stress unit 30. The respective units make a snug fitaround the insulation 11 which, due to its compressible character,provides a suitable medium to take care of any radial expansion due toheating of the cable proper. Each axial condenser unit 32 is connectedelectrically in series with its adjacent units. This is accomplished byproviding each grading tube 32 with two separate helically coiled metalgarter springs 56 each formed as an end less ring and embracing themetal glaze on the cylindrical portion of the grading .tube, one belowand one above the flange 42. Each spring is stretched and thereforetensioned by the cylindrical body of the capacitor grading tube, so thateach spring remains in place and in electric contact with the conductivecoating on the tube. Connection between adjacent condensers is formed byshort braided copper or bronze jumper leads 58 each of which is solderedor otherwise electrically secured at its opposite ends to springs onadjacent capacitor grading tubes, as may be seen from Figures 1 and 2.The lowermost grading tube 32 is connected at its bottom half by ajumper lead 58, to a spring 60, identical with the spring 56, thatsurrounds and is tensioned around the conducting coating 39 on thelowermost radial stress unit 30, said spring being also connected by asimilar jumper lead 62 to one of the grounded bolts 22. The uppermostspring of the series of capacitor grading tubes is connected by a jumperlead 66 to a metal yoke 63 that rests upon the upper flange of theuppermost grading control unit 32, and is electrically connected to thecable conductor. It is thus apparent that the capacitor grading tubesare connected in series between ground potential at their lower ends andthe conductor potential at their upper ends. The bight portion 69 of theyoke 68 has a centrally located hole therethrough through which extendsa metal connector stud 70 that is mechanically and electrically securedto the end of the cable conductor 3. The yoke 68 is pressed downwardlyby a coiled spring 72 that bears at its lower end at the top of the yokeand at the upper end is received in a cap 74 that is held in position bya nut '76 threaded on the stud 70. The spring 72 acting through the yoke68 presses against the top of the uppermost potential grading tube 32and maintains all of the grading tubes and the lowermost stress unit St)in engagement on the seat of the seating ring 23 during assembly of thepothead. This stress is taken over by the insulator 27 and the base andcap assembly when the pothead has been assembled.

For mechanical simplicity all of the capacitor grading units '32 may beof identical construction. However, as pointed out previously, there isan electrical advantage 1n making these control units of diiferentcapacities rangmg from a maximum capacity of the lowermost unit 32 and aminimum capacity of the uppermost unit 32. The variation in capacity isobtained by making the flanges 42 of the respective units of diiferentthicknesses, the flange 42 of the lowermost unit being of minimumthickness and the corresponding flange of the uppermost unit being ofmaximum thickness, with the flanges of the intervening units ofthicknesses grading between In one preferred construction, which is theone here described, the radial capacity for the unit 30 and for each oneof the units 32 was 11.5 micromicrofarads, and the axial capacitybetween the conductor surfaces 47-47 of the lowermost unit 32 was 2400micromicrofarads, and the capacity between the conductive glazedsurfaces 47-47 of the uppermost or line voltage control unit 32 was 200micromicrofarads, and the capacities between the surfaces 47-47 of theintervening units graded between those two values.

The upper portion of the pothead is sealed in any conventional manner,for instance, as shown in my pending application Serial No. 219,294above referred to, to which reference may be had. This seal consists ofa cap assembly which includes a metal hood 86 having a closed thin metaltube 88 in which the stud makes a sliding fit, thetube being thencompressed on the stud to establish proper electrical and mechanicalconnections. The upper end of the stud has longitudinal slots therein topermit fluid to flow past the stud within the tube 88, as may berequired during formation of the pothead. The hood '86 rests on and issealed over the upper end of the insulator 27, a suitable frusto conicalsealing gasket 89 being interposed to facilitate the sealing action. Aunitary ring 90, which is suitably secured to the bottom of the hood,provides means for bolting the hood to a unitary ring 92 that iscemented around the top neck of the insulator 27, all as shown in myaforesaid application. 'The usual metal corona shield 94 is provided.The hood has a tapped boss 95 for receiving fittings used duringinstallation.

. Reference may now be had more particularly to Figure which shows anenlarged cross sectional view through the cable conductor and thegrading tube 30 or the lower half of the bottom unit 32, and shows thevoltage gradient, in percentage, from the outer surface of the cableconductor, through the cable insulation and through the grading tube tothe potential on the glaze 46 of the tube 32, which is ground potentialin the case of the lowermost tube 32. If we assume that the insulationbetween the cable conductor and the grading tube 32 has a specificinductive capacity of 4 and that the specific inductive capacity of theinsulation of the tube 32 is 100, then the voltage distribution startingat 100% cable conductor voltage at the periphery of the cable conductor3, as indicated by the ordinate line 101, is indicated by the curve 100,progressing downwardly along the curve until at the inner periphery ofthe tube 32 the voltage, indicated at 102, is 0.5% of the total voltagebetween the cable conductor and the metallic glaze 46 on the outside ofthe tube 32. From the point 102, which indicates a voltage of 0.5% onthe inner surface of the body of insulation 40 of the tube 32, thevoltage gradient then follows along the line 104 through the thicknessof the insulation 40 to the potential of the conducting glaze 46. It isthus apparent from the curve of Figure 5 that the potential on the innersurface of the respective grading tubes 32 is only 0.5% of the voltageon the outside of the potential grading tube, so that within the potheadinsulator 27 the potential on the outer surface of the wrappedinsulation around the cable conductor is, at each point of the axiallength thereof, at a value substantially equal to that of the adjacentouter condenser plate 46 or 46. Since the capacitor grading tubes 32 arearranged to provide a uniform stepped voltage stress distribution fromthe line voltage at the top of the pothead to ground voltage at thebottom theref, it is thus apparent that substantially the same voltagedistribution is obtained along the axial length of the cable conductorcovering insulation.

Reference may now be had more particularly to Figure 6 which shows theapproximate distribution of the equipotential lines in the pothead abovedescribed. In this pothead the ten capacitor grading tubes 32 are ofidentical heights and the ilanges 42 of the respective ones thereof areof different thicknessses to give an axial capacity of 2400micromicrofarads for the bottommost tube '32 and 200 micromicrofaradsfor the uppermost tube 32, as set forth above. The total axialcapacitance, namely, the equivalent capacity of the group ofcapacitances 32 in series are such that the capacity current controllingthe voltage division is not appreciably affected by external straycapacities and leakage currents. The axial capacity current is made tobe of the order of one to five milli-amperes, depending upon surfaceconditions and voltage rating. The equipotential lines 111 to 120 arelines from 5% to of the line to ground voltage in uniform steps of 10%between successive ones of the lines 111 to 120. These lines show therelative uniform axial distribution of the voltage both in the internaldielectrics as well as in the external dielectric.

In considering the flow of capacity current through the connectedcondensers of the respective capacitor grading tubes 32 there are anumber of factors that must be borne in mind. One is the usual currentflow through the condensers that are connected in series from the linepotential to the ground potential as determined by what might be calledthe axial capacity of the respective units. Another is the fact thatcapacitance exists between each unit capacitor and the insulated cableconductor that passes within it. This may be referred to as the radialcapacity as distinguished from the axial capacity. It is apparent thatall of the units are required to carry the capacitance current resultingfrom the axial capacity and that the capacitor units 32 near thegrounded end of. the structure would be required to carry more of theradial capacitance current than is required of those units 32 that arenearer the conductor or line potential end, since the radial capacitancecurrent at any point of the cable flows to ground only through thoseunits 32 between. that point and ground. This increased current passingthrough the lower units would normally tend to produce a greatedpotential drop across the lower units 32 than the potential drop acrossthe units 32 nearer to the top of the pothead. Therefore, a uniformpotential gradient would not be obtained with uniform axial capacity inthe respective capacitor grading tubes 32. By having the capacitor unitsof progressively increasing values between the line end and the groundedend, and properly graded, a uniform voltage division between therespective grading tubes 32 and the flange 42 of each such unit isobtained.

It is desirable that individual capacitor sections 32 be employedbecause this simplifies manufacturing problems and permits productiondielectric testing of the respective units and capacity adjustment inassembling units of different capacities. However, a one-piececonstruction of two or any other number, up to all, of the units 32,with or without the unit 30, may be provided in which the equivalentcondensers formed at the respective flanges 42 of that unit areelectrically in series the same as the different units 32. This isillustrated in a fragmentary manner in Figure 7, wherein the unit,indicated at 32a, comprises two or more, up to all, of the units 32 ofFigures 1 and 2. The parts of Figure 7 that are the same ascorresponding parts of the unit of Figure 3 have been designated by thesame reference numerals with the subscript a added to designate thisalternate structure.

The high voltage pothead described above is primarily adapted for use oncable systems which are of the high internal hydraulic or gas pressuretype. The principles can, however, be applied to potheads for lowpressure systems. In the design of such systems there is much greaterleeway as to the outer porcelain bore diameters, since these diametersare not limited by the porcelain rupture stresses involved on the highpressure systems.

In compliance with the requirements of the patent statutes I have hereshown and described a preferred embodiment of my invention. It is,however, to be understood that the invention is not limited to theprecise construction here shown, the same being merely illusavs gosstrative of the principles of the invention. What I consider new anddesire to secure by Letters Patent is: 1. An electric condensercomprising an open ended sleeve through which a'high voltage conductormay be extended, said sleeve having a thin radially outwardly extendingsurrounding flange, the sleeve and the flange constituting one integralbody of insulation, and separate unconnected metallic conducting areascovering the opposite surfaces of the flange to form two conductingareas constituting opposite plates of a condenser, and at least one ofsaid conducting areas extending also along the outer surface of thesleeve to form a capacity coupling with a high voltage conductor thatmay be extended axially through the sleeve.

2. An electric condenser comprising an open ended sleeve through which ahigh voltage conductor may be extended, said sleeve having a radiallyoutwardly extending surrounding flange intermediate the ends thereof,which flange in turn is surrounded by a rim, the sleeve and the flangeand the rim constituting one integral body of insulation, and separatemetallic conducting areas covering the opposite surfaces of the flangeand each terminating at its outer periphery at said rim so that the twoconducting areas constitute opposite plates of a condenser, and each ofsaid conducting areas extending also along the outer surface of thesleeve to form a capacity coupling with a high voltage conductor thatmay be extended axially through the sleeve, the opposite ends of thesleeve being flat planar surfaces to permit stacking of similarcondenser units one upon another.

3. An electric condenser comprising an open ended sleeve through which ahigh voltage conductor may be extended, said sleeve having a radiallyoutwardly extending surrounding flange intermediate the ends thereof,which flange in turn is surrounded by a rim, the sleeve and the flangeand the rim'constituting one integral body of insulation, and separatemetallic conducting areas covering the opposite surfaces of the flangeand each terminating at its outer periphery at said rim so that the twoconducting areas constitute opposite plates of a condenser, and each ofsaid conducting areas extending also along the outer surface of thesleeve to form a capacity coupling with a high voltage conductor thatmay be extended axially through the sleeve, the opposite ends of thesleeve being flat planar surfaces to permit stacking of similarcondenser units one upon another, and means for connecting the condenserin a circuit comprising two metal helical springs each coiled to form anendless ring that are tensioned respectively around the conducting areason the sleeve on opposite sides of the flange.

4. An electric condenser comprising an open ended sleeve through which ahigh voltage conductor may be extended, said sleeve having a radiallyoutwardly extending surrounding flange intermediate the ends thereof,which flange in turn is surrounded by a rim, the sleeve and the flangeand the rim constituting one integral body of insulation, and separatemetallic conducting areas covering the opposite surfaces of the flangeand each terminating at its outer periphery at said rim so that the twoconducting areas constitute opposite plates of a condenser, and each ofsaid conducting areas extending also along the outer surface of thesleeve, and means for establishing electrical connections to saidconducting areas comprising metallic helical springs coiled to formseparate endless rings, the respective rings being tensioned around theconducting areas of the sleeve.

5. An electric condenser comprising an open ended sleeve through which ahigh voltage conductor may be extended, said sleeve having a radiallyoutwardly extending surrounding flange intermediate the ends thereof,which flange in turn is surrounded by a rim, the sleeve and the flangeand the rim constituting one integral body of insulation, and separatemetallic conducting areas covering the opposite surfaces of the flangeand each terminating at its outer periphery at said rim so that the twoconducting areas constitute opposite plates of a condenser, and each ofsaid conducting areas extending also along the outer surface of thesleeve to form a capacity coupling with a high voltage conductor thatmay be extended axially through the sleeve, the opposite ends of thesleeve being flat planar surfaces to permit stacking of similarcondenser units one upon another, and means for connecting two suchcondenser units in series comprising two metal helical springs eachcoiled to form an endless ring that are tensioned around the respectivesleeves.

6. In combination with a current carrying conductor, a condenser elementformed by an open ended insulating sleeve surrounding said conductor,said sleeve having a radially outwardly extending. surrounding flange ofinsulating material formed intermediate its ends and separate conductiveareas on the outer surface of said sleeve, the ends of said sleeve eachbeing flat to facilitate coaxial stacking of similar condenser elements,said conductive areas covering the opposite surfaces of said flange toform two spaced conducting members constituting opposite plates of acondenser and said flange of insulating material forming a condenserdielectric, and each of said conducting areas extending also along theouter surface of the sleeve into capacitive coupling relationship withsaid current carrying conductor, whereby said conductor and said portionof the conductive areas surrounding said sleeve forming respectivecondensers which in turn are electrically connected with saidfirst-mentioned condenser.

7. A condenser assembly comprising a pair of stacked condenser elementseach of which comprises an open ended sleeve of insulating materialhaving a radially outwardly extending surrounding flange intermediateits ends, said sleeves also having respective end flanges at theiropposite ends which project a lesser amount from the sleeves than saidfirst-mentioned intermediate flange, and separate conductive areas onthe opposite sides of the intermediate flange of each sleeve, saidconductive areas extending from the end flanges of each sleeve along thebody of the sleeve and along the opposite surfaces of said intermediateflange to form opposite plates of a condenser separated by a dielectricconstituted by said intermediate flange, and means for electricallyconnecting said two stacked condensers comprising two metal helicalsprings each coiled to form an endless ring which are tensionedrespectively around the adjacent conductive portions of said respectivesleeves and a jumper lead electrically connecting said helical springs.

8. An electric condenser comprising an open ended sleeve having acylindrical inner surface forming a bore through which a high voltageconductor may be extended, said sleeve having a thin radially outwardlyextending surrounding flange, the sleeve and the flange constituting oneintegral body of insulation, and separate unconnected metallicconducting areas covering the opposite surfaces of the flange to formtwo conducting areas constituting opposite plates of a condenser, saidsleeve having an outer surface parallel to the inner cylindrical surfacefor a substantial fractional part of the axial length of the sleeve, andat least one of said conducting areas extending also along the outersurface of the sleeve to form a capacity coupling with a high voltageconductor that may be extended axially through the sleeve.

9. An electric condenser comprising an open ended sleeve through which ahigh voltage conductor may be extended, said sleeve having a radiallyoutwardly extending surrounding flange intermediate the ends thereof,which flange in turn is surrounded by a rim, the sleeve and the flangeand the rim constituting one integral body of insulation, the sleevebeing of uniform thickness for a substantial portion of its length onopposite sides of the flange, and separate metallic conducting areascovering the opposite surfaces of the flange and each terminating at itsouter periphery at said rim so that the two conducting areas constituteopposite plates of a condenser, and each of said conducting areasextending also along the outer surface of the sleeve to form a capacitycoupling with a high voltage conductor that may be extended axiallythrough the sleeve, the opposite ends of the sleeve being fiat planarsurfaces to permit stacking of similar condenser units one upon another.

10. In combination with a current carrying conductor, a condenserelement formed by an open ended insulating sleeve surrounding saidconductor, said sleeve having a radially outwardly extending surroundingflange of insulating material formed intermediate its ends and separateconductive areas on the outer surface of said sleeve, the ends of saidsleeve each being flat to facilitate coaxial stacking of similarcondenser elements, said conductive areas covering the opposite surfacesof said flange to form two spaced conducting members constitutingopposite plates of a condenser and said flange of insulating materialforming a condenser dielectric, said sleeve being of uniform thicknessfor a substantial portion of its length on opposite sides of the flange,and each of said conducting areas extending also along the outer surfaceof the sleeve 10 into capacitive coupling relationship with said currentcarrying conductor, whereby said conductor and said portion of theconductive areas surrounding said sleeve forming respective condenserswhich in turn are electrically connected with said first-mentionedcondenser.

References Cited in the file of this patent UNITED STATES PATENTS1,868,962 Atkinson July 26, 1932 1,870,141 Regerbis Aug. 2, 19321,878,169 Myers Sept. 20, 1932 2,065,921 Gerth Dec. 29, 1936 2,161,326Webb June 6, 1939 2,251,540 Buschbeck Aug. 5, 1941 2,297,200 BuschbeckSept. 29, 1942 FOREIGN PATENTS 601,961 Germany Aug. 28, 1934 478,602Great Britain Ian. 21, 1938 1,000,191 France Oct. 10, 1951 1,010,397France Mar. 26, 1952

